Horde IMP 4.3.6 and earlier does not request that the web browser avoid DNS prefetching of domain names contained in e-mail messages, which makes it easier for remote attackers to determine the network location of the webmail user by logging DNS requests.

Multiple cross-site scripting (XSS) vulnerabilities in Horde IMP H3 4.1.3, and possibly earlier, allow remote attackers to inject arbitrary web script or HTML via (1) the email Subject header in thread.php, (2) the editquery parameter in search.php, or other unspecified parameters in search.php. NOTE: some of these details are obtained from third party information.

Cross-site scripting (XSS) vulnerability in fetchmailprefs.php in Horde IMP before 4.3.8, and Horde Groupware Webmail Edition before 1.2.7, allows remote attackers to inject arbitrary web script or HTML via the fmid parameter in a fetchmailprefssave action, related to the Fetchmail configuration.